sanders



March 17, 1964 G. J. SANDERS 3,125,286

SILENT VENTILATOR SYSTEM Filed Feb. 4, 1960 s sheets-sheet 1 G. J. SANDERS SILENT VENTILATOR SYSTEM March 17, 1964 Filed Feb. 4, 1960 s sheets-sheet 2 v n KSQ Fig. 7.

Fig. 9.

lNvENToR Guy d. Sanders March 17, 1964 G. J. SANDERS 3,125,286

SILENT VENTILATOR SYSTEM Filed Feb. 4, 1960' 5 sheets-sheet 3 Frequency in Cycles per Second Reference Pressure Leve| Spectrum Sound Pressure in Decbles-Re. 0.0002 Dyne/CM2 2C Sound Pressure V Levels with INVENTOR lo Venillotor Operating k"` GUY SANDERS Ociove Bonds Cycles per Second TTORNEYS United States Patent C) Fice Acoustics Company, Inc., New York, N.Y., a corpora tion of New York Filed Feb. 4, 1960, Ser. No. 6,826 6 Claims. (Cl. 2250-233) This invention relates to a ventilator system and more particularly to a forced air ventilator having sound attenuating properties.

It is known in the construction of ventilators to include, either integrally or as separate components, devices for attenuating the generation and transmission of noises associated with the movement of the uid medium in the ventilator. Principal design criteria in such ventilators are directed towards providing an adequate ventilating function. Acoustic factors, in contrast, are treated as ancillary features. In the main, the basic design is directed toward ventilation and this design is then modified by superimposing acoustic elements thereon in order to alleviate the generation and transmission of noise. This approach, while satisfactory for the usual home, oiiice and plant installation, is grossly inadequate in those areas where special acoustic conditions are desired. In audiometric installations, eg., in areas where auditory testing is practiced and in certain research labs, it is necessary that noise be reduced below certain predetermined levels. ln these special cases the usual ventilator is completely inadequate in view of the noise and vibration it generates and/or transmits. Thus, a typical Ventilating system could not be used in an anechoic chamber where audio components are tested since the noise associated with the ventilator would corrupt the very conditions achieved by the special design of the enclosure.

In view of the inapplicability of conventional ventilators to the above situations, it has been the practice of the art to employ a special arrangement in which the fan or other impeller which is to be used for Ventilating is located externally of the conditioned room and is completely isolated from all structures which are coupled to the conditioned room. Thus, the impeller is generally in an adjoining room and is so mounted as to be physically isolated from the walls, ceiling and oor thereof so as to prevent transmission of noise and vibration from the fan to the conditioned room. The impeller is also encased in a sound attenuating enclosure and connected thereto is a duct which frequently consists of a flexible hose. The outlet end of this hose is connected at an inlet in the conditioned room. This inlet within the conditioned room is also subjected to extensive acoustic treatment.

The above described arrangement does not provide an optimum ratio of ventilation to noise attenuation. It is also complicated and cumbersome and lacks an integral character. The dissociation of parts requires that each be separately and individually'treated with acoustic materials and techniques, thereby precluding synergetic effects. Moreover, the parts cannot be optimally designed since their physical relationship to one another is not fixed. This separation of parts requires a cut and try approach in the installation of the system to find a reasonably satisfactory physical association of the components. In many cases the installation is also aesthetically displeasing and wastes considerable space.

It is thus an object of the invention to provide a substantially silent ventilator having an attendant noise spectrum less than the maximum permissible ambient spectrum of acoustic rooms, labs and enclosures.

It is another object of the invention to provide a substantially silent ventilator which is of an integral nature.

Another object of the invention is to provide a ventilating system in which the noise and vibration associated 3,125,286 Patented Mar. 17, 1964 with operation of the ventilator is below the threshold sensitivity of the ear.

It is another object of the invention to provide a ventilator which has greater Ventilating capacities than presently used ventilators of comparable size and which provides at the same time, improved acoustic performance.

It is another object of the invention to provide a substantially silent ventilator in a single integrated and unitary arrangement comprising essentially one piece of equipment.

It is a further object of the invention to provide such a ventilator which may be readily installed in manifold configurations and which requires an extremely simple installation procedure.

It is a further object of the invention to provide such a ventilator having a heretofore unattainable ratio of air iiow to noise level, a ventilator which by virtue of its structural arrangement has inherent durability and reliability and one in which relatively inexpensive components are employed.

A further object of the invention is the provision of an integral ventilator which may be mounted on a wall of the ventilated enclosure and which does not transmit vibrations to the treated enclosure.

An additional object of the invention is to provide a ventilator of such an integral and compact character as to enable a plurality thereof to be readily combined in a single installation.

These and other objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

Briefly and generally, the invention comprises a single cabinet or casing which encloses a specially configured duct and fan assembly. One end of the duct is designed to communicate with the room to be conditioned while the other end thereof communicates with an external area or enclosure. The ventilator may be operated to either supply conditioned air to the subject room or to exhaust air therefrom, and regardless of its mode of operation, the noise level attending operation of the ventilator is below the threshold sensitivity of the ear.

The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.

An embodiment of the invention is described in the accompanying specification and illustrated in the accompanying drawings of which:

FIGURE l is an elevation view partly in section of the ventilator installed on a wall of the conditioned room;

FIGURE 2 is a plan view of the embodiment of FIG- URE l;

FIGURE 3 is a side elevation view partly in section of the arrangement of FIGURE l;

FlGURES 4 and 5 are cross-sectional views taken along lines 4 4 and 5 5 of FIGURE 3;

FIGURES 6, 7 and 8 are details of the fan mounting assembly;

FIGURE 9 is a detail of a closure plate attached to the ventilator structure;

FIGURE 10 is a graph illustrating performance of the embodiment of the invention contrasted with a reference spectrum; and

FIGURE ll is another graph illustrating performance of the embodiment contrasted with other reference spectra.

As seen in FIGURE l, there is attached to wall, ceiling or oor 1t), the room ventilator 12. The casing 13 of the ventilator is of generally rectangular shape, is preferably steel, and defines, in combination with its internal liner, a duct 14 having an external outlet 15 and a room outlet 16. The duct 14 comprises a tandem or serial array of five sections, 14a, 14b, 14e, with section 14h housing a special axial vane fan 18. Over the external outlet 15 a sliding closure plate 19 (FIGURES 2, 9) is mounted, the plate being slidably, but otherwise tightly confined by a pair of flange-tracks 20, suitably secured as by brazing or welding to casing 13. A handle 19a integral with plate 19 is provided for adjustment of the air flow through the ventilator. Over the room outlet 1-5, a felt pad 21 is provided, the pad being cemented to the room side of casing 13. The pad has a cutout for the passage of air and since it is pressed between the casing 13 and the structure 10, it functions as a seal against spurious air and sound transmission.

For mounting ventilator 12 to structure 10, the casing 13 includes a flange 23 integral with the sides and one end of the ventilator and provided with mounting holes 24 and 24', the latter being lined with rubber grommets. An additional grommet 25, FIGURES 2, 5, is seated in a passageway in the casing adjacent a transverse flange 27. This passageway receives the power cable for the fan 18. The flange 27 is formed from the junction of the two sections of the casing, a two piece construction being employed to permit servicing and replacement of fan 18.

Also functional in the installation arrangement are a pair of sponge rubber pads, 28, which serve to isolate the ventilator from the structure 10. The rubber grommets in mounting holes 24' also contribute to this function in isolating the ventilator from the mounting screws tapped into structure 10. While the felt pad 21 at one end of the ventilator does' provide some isolation, this end, being relatively remote from fan 18, does not require the same isolation as provided at the other end of the ventilator. As noted hereinafter, the simplicity of the entire isolation arrangements results in part from other features of the duct.

Lining the entire inside of casing 13, except at outlets 15 and 16, is a coat of sheetrock, formed from continuous pieces 30a, 30b, 30e, 30d (FIGURE 3) and 30e, 30]c (FIGURES 4, 5), the pieces being secured to the casing by roof cement or the like. Continuous pieces of sheetrock rather than fragments are preferred. The sheetrock provides effective attenuation of sound which tends to be transmitted between the ventilator, the casing 13, and the exterior thereof including the area in which the ventilator is housed and the structure 10.

The duct 14 of the ventilator is disposed therein in a generally symmetrical configuration except for the oppositely turning regions of the outlet sections 14a and 14e. These turns, in addition to supplying the general configuration required for most installations, also provide certain acoustic features as noted hereinafter.

The duct is bounded on all sides of sections 14a, 14C and 14d and on the top and bottom surfaces of section 14e, with perforated sheets 31, preferably galvanized steel. As seen in FIGURE 4, the other surfaces of section 14e are bounded by the sheetrock strips 30e and 30f. The sheetrock in this respect provides the dual functions of attenuating both structure-borne and air-borne noise.

Four perforated sheets 31 which delineate section 14a of the duct are turned at right angles in the region adjacent section 14b and also in the region of outlet 15. The sheets 31 which border sections 14c and 14d are similarly turned in the region of section 14b and two of these sheets are also flanged at their sides and at outlet 1 6. Except for the latter two cases, the sheets have flared ends in the region where they are turned in order to form continuous flanges. This orientation of the lsheets, in cooperation with the sheetrock layers 30a, 3017, 30), forms compartments 33, 34 and 35 which are filled with an acoustically absorbent material 36, vpreferably spun felt.

Considering now the fan assembly, it is first noted that section 14b which houses this assembly is effectively isolated from section 14a by virtue of the premature termination of the perforated sheets 31 in the latter section. There is thus provided a space' 38 between the two sections which is only broken by the slieetrock and external casing. In addition and as described below, the fan per se is isolated from its own compartment, 14b, by an assembly of isolaters 39 and 40. These arrangements isolate the fan on both the acoustic and vibration (dynamic) basis.

The fan 18, termed a venturi fan, has three wide blades and no external motor. The motor is rather housed within the hub of the fan and the resultant configuration has a flat, low-amplitude noise spectrum. It generates less low-frequency noise but more high-frequency noise than many fans used for a comparable purpose, especially centrifugal types. Its high-frequency characteristic may be attributed in part to the high operating speed of the fan, eg., 3600 r.p.m. A fan of this type is disclosed in U.S. Patent 2,855,141. The fan mounting assembly includes rectangular isolater 39 (FIGURES 3, 6 and 8), preferably polyurethene rubber which is sandwiched between isolaters 40 (FIGURES 3, 7 and 8), these also being preferably fabricated from polyurethene rubber. A square cutout in isolater 39 and circular cutouts in isolaters 40 form the longitudinal surfaces of duct section 14h in which the fan operates'. The isolaters 39, 40 are secured together, as by cementing (FIGURES 3, 8), with the fan in its rectangular housing 50 being positioned inside this combination. The hollow interior of housing 50 is of cylindrical cross-section. The fan is coupled thereto by four struts 51 which radially extend from the fan to the corners of the housing. The isolater assembly is press fitted within the sheetrock liner 30a, 30C, 30e, 301, of casing 13, Contact therebetween being effected by projections 45, integral with isolater 40 (FIGURE 7). Mini mum contact between the fan assembly and the ventilator casing is thus provided.

In operation, closure plate 19 is adjusted along the tracks 20 to obtain the desired opening of the duct. There.- after fan 18 is energized and operated in a clockwise or counterclockwise direction according to whether air is supplied to the conditioned room or exhausted therefrom. This air is supplied at a rate (e.g. c.f.m.) which is substantially greater than comparable sized units. Even with this increased rate, the acoustic properties of the ventilator are such that whether air is being supplied or exhausted, no discernible noise is coupled to the conditioned room.

This performance, which has not been attained heretofore in any ventilator of comparable weight, space, simplicity and cost, results from the nature of the ventilator components and from their cooperation. Thus, the lownoise and vibration characteristic of the fan assembly contributes to the adaptability of the ventilator to direct mounting on the Wall of the conditioned enclosure without the need for extensive isolating arrangements. The effectiveness of the simple isolating assembly 39, 40, the sheetrock liner 30a, 30]: 30f, the isolation pads 28, and the cooperating mounting elements is thus substantially enhanced. The mid and high-frequency components of fan noise, especially the latter, are effectively eliminated by the absorbent lined duct and by the bends therein. This arrangement also substantially eliminates noise generated by other causes. The duct 14 also includes a section 14e which has a high perimeter/ area ratio (P/A) to provide optimum per unit length attenuation and also includes an absorbent lined duct section and bend 14a which, in addition to attenuating noise transmission into the treated room, also attenuates noise tending to develop in the area adjacent the outlet 15. For smooth laminar flow in the duct, a transition region 14d is also provided therein.

Indicia reflecting the performance of the embodiment of the invention are provided in the graphs of FIGURES l0 and 1l, the coordinates of which represent respectively, sound pressure in decibels, referenced to 0.0002 dynes per cm.2 and frequency, in cycles per second.

In the graph of FIGURE 10, the spectrum V of the instant ventilator is plotted along with a reference spectrum. Plot V comprises sound pressure levels at the indicated frequencies, with the ventilator operating, measured at a persons ear level, where the person is seated near the window (three feet from blower inlet) in a standard room.

The reference spectrum of FIGURE l0 represents the suggested spectrum for maximum background noise for reliable industrial hearing tests, suggested by Dr. Aram Glorig, Director of Research, American Academy of Opthalmology and Otolaryngology.

The pressure levels V in the figure have been extrapolated between the octave bands 300-600 and 60G-1200 and remain substantially below the reference levels. The decreasing trend continues above these frequencies, the levels actually falling to negative values in the higher bands. (This may be verified by reference to FIGURE 11.) It is clearly evident in FIGURE that the invention provides a ventilator which more than satisiies the above noted criteria for industrial hearing tests.

In FIGURE 11 a logarithmic plot of the performance V1 of the ventilator is contrasted with threshold curves relating to monaural minimum audible pressure, curve R2, and binaural minimum audible iield, curve R3. Plot V1 was obtained under the same conditions as existed in obtaining plot V of FIGURE 10. That the ventilator meets the criteria for sub-threshold sound generation is amply established by the data of FIGURE 11.

With a view towards expediting the practice of the invention, exemplary data is provided hereinbelow:

Typical Specification:

(Dimensions in inches unless otherwise noted)' Casing 9 x l2 (incl. flange) x 75.

#16 gauge CRS. Duct:

Section 14a Inside radius l.

Outside radius corner) 41/2 Cross-section 41/2 x 41/2.

Length in plan l2.

41/2 x 41/2 x 4. Length-4.

Inside radius 31A. kOuside radius 4% Cross-section 11/2 x=8%s.

(from proj.

Section 14C Section 14d Section 14e Isolators:

Isolator 39 6 x 7 x 11/2.

Cutout 41/2 x 41/2.

Isolators 40 6 x 7 x l with l x 2 extensions on each side. Cutout radius 2%.

Duct Liner #22 gauge galv. perf. steel.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A substantially noiseless integral, forced-air ventilator comprising a casing, a first aperture in one side of said casing and a second aperture in another side of said casing, substantially bathe-free duct means within and spaced from said casing comprising a first section communicating with said rst aperture, a second section communicating with said second aperture and a central section communicating with said first and second sections, isolating means, an impeller mounted on said isolating means in the region of and communicating with said central section whereby said impeller is acoustically and dynamically decoupled from said central region, acoustic absorbent means in said space between said casing and said duct sections, one of said sections having a single passageway of high perimeter area ratio, one of said sections including a bend, and said isolating means cornprising a resilient impeller member sandwiched between a plurality of resilient mounting members, said impeller being mounted in said impeller member, said mounting members including integral resilient appendages for holding said mounting means in said ventilator.

2. A substantially noiseless, integral forced-air ventilator comprising a ventilator casing, iirst and second apertures in said casing, duct means within said casing, said duct means being oriented to provide communication between said first and second apertures, an axial Vane impeller in said casing, said axial vane impeller being mounted in a hollow central section of a plane resilient medial member, said member being sandwiched between plane resilient boundary members, said boundary members each including a plurality of integral extensions adapted to resiliently secure said members within said casing in a position which interposes said impeller in said dudt means.

3. A forced-air ventilator having a noise spectrum below the aural threshold spectrum of a human comprising a casing, iirst and second apertures in said casing, duct means lined with acoustically absorbent material within said casing, said duct means comprising a first duct section communicating at one end thereof with said first aperture and at another end thereof with a second duct section, said iirst section including a bend therein and said second section including impeller means, a third duct section communicating at one end thereof with said second section and at another end thereof with a fourth duct section, said fourth section being of decreasing cross-section and communicating at one end thereof with a fifth duct section, said fth section having a high perimeter/ area ratio region and a bend therein, said fth section communicating with said second aperture.

4. A ventilator according to claim 3, in which said vend in said first section comprises substantially a right angle.

5. A ventilator according to claim 3, in which said second, third and fourth sections are substantially void of bends while said rst and iifth sections each include a substantially right angle bend.

6. A ventilator according to claim 3, in which said rst, third, fourth and iifth duct sections are substantially void of baffles and include perforated duct walls backed by an acoustically absorbent material.

References Cited in the iile of this patent UNITED STATES PATENTS 644,106 Smead Feb. 27, 1900 1,473,648 Scherer Nov. 13, 1923 1,916,908 Stacey July 4, 1933 1,964,845 Dietze et al July 3, 1934 2,020,092 Allen Nov. 5, 1935 2,028,985 Mahon Jan. 28, 1936 2,161,027 Dollinger June 6, 1939 2,247,121 Foldes June 24, 1941 2,433,544 Blake et al Dec. 30, 1947 2,674,405 Cawl Apr. 6, 1954 2,745,509 Argentieri May 15, 1956 2,749,024 Wilfert June 6, 1956 2,855,139 Wiebel Oct. 7, 1958 2,869,535 Horrell Jan. 20, 1959 2,885,142 Eberhart May 5, 1959 2,943,695 Jeffords July 5, 1960 2,996,973 Boysen Aug. 22, 1961 FOREIGN PATENTS 58,806 France Nov. 25, 1953 

1. A SUBSTANTIALLY NOISELESS INTEGRAL, FORCED-AIR VENTILATOR COMPRISING A CASING, A FIRST APERTURE IN ONE SIDE OF SAID CASING AND A SECOND APERTURE IN ANOTHER SIDE OF SAID CASING, SUBSTANTIALLY BAFFLE-FREE DUCT MEANS WITHIN AND SPACED FROM SAID CASING COMPRISING A FIRST SECTION COMMUNICATING WITH SAID FIRST APERTURE, A SECOND SECTION COMMUNICATING WITH SAID SECOND APERTURE AND A CENTRAL SECTION COMMUNICATING WITH SAID FIRST AND SECOND SECTIONS, ISOLATING MEANS, AN IMPELLER MOUNTED ON SAID ISOLATING MEANS IN THE REGION OF AND COMMUNICATING WITH SAID CENTRAL SECTION WHEREBY SAID IMPELLER IS ACOUSTICALLY AND DYNAMICALLY DECOUPLED FROM SAID CENTRAL REGION, ACOUSTIC ABSORBENT MEANS IN SAID SPACE BETWEEN SAID CASING AND SAID DUCT SECTIONS, ONE OF SAID SECTIONS HAVING A SINGLE PASSAGEWAY OF HIGH PERIMETER AREA RATIO, ONE OF SAID SECTIONS INCLUDING A BEND, AND SAID ISOLATING MEANS COMPRISING A RESILIENT IMPELLER MEMBER SANDWICHED BETWEEN A PLURALITY OF RESILIENT MOUNTING MEMBERS, SAID IMPELLER BEING MOUNTED IN SAID IMPELLER MEMBER, SAID MOUNTING MEMBERS INCLUDING INTEGRAL RESILIENT APPENDAGES FOR HOLDING SAID MOUNTING MEANS IN SAID VENTILATOR. 